The chief of Algeria's national police force has been shot dead at his headquarters by another police official.

Ali Tounsi was killed by a colleague during a regular morning meeting in the police headquarters in front of several witnesses. "It took place during a working session, in the course of which a police official, apparently gripped by an attack of madness, used his weapon and fatally wounded Colonel Tounsi," the interior ministry said.

"A judicial inquiry has been opened to determine the circumstances of this distressing event," the statement said. There was no indication of any link between Colonel Tounsi's killing and al-Qa'ida insurgents who periodically attack government targets in Algeria, a major oil and gas exporter.

The police force headed by Colonel Tounsi has played an important role in the effort to stamp out the long-running insurgency by Islamist militants. Earlier, a security source told Reuters that Colonel Tounsi, national police chief for more than a decade, was shot inside his office by a senior police official with whom he was having an argument.

"This guy was unhappy, he took out his pistol and he fired it," the source said. "Police officers nearby fired back."

The interior ministry statement said that after shooting the police chief, the attacker shot himself and was now in a serious condition in hospital. It made no mention of police firing back.

It is unlikely that Colonel Tounsi's killing will be a significant setback for the counter-insurgency, which has been successful in reducing the rebellion to a hardcore of a few hundred fighters.

"Tounsi's death is a big loss but it won't have any impact on the fight against terrorism," an official source familiar with security issues said.